Computer security is fast becoming an important issue. With the proliferation of computers and computer networks into all aspects of business and daily life--financial, medical, education, government, and communications--the concern over secure file access is growing. One method of providing security from unauthorized access to files is by implementing encryption and cipher techniques. These techniques convert data into other corresponding data forms in a fashion that is reversible. Once encrypted, the data is unintelligible unless first decrypted. RSA, DES, PGP, and CAST are known encryption techniques that are currently believed to provide sufficient security for computer communication and files.
Each of the encryption techniques uses a key or cipher. Such a key is crucial to the encryption/decryption process. Anyone with a correct key, can access information that has previously been encrypted using that key. The entry of the key from the keyboard is impractical since a key remembered by a user for entry is liable to be discovered by an individual desiring unauthorized access to existing encrypted files.
In DES encryption, the key is a numerical value, for example 56 bits in length. Such a key can be used to encrypt and subsequently to decrypt data. The security of the data once encrypted is sufficient that the key is required to access the data in an intelligible form. Thus, the security of the data is related to the security of the key.
In an optical fingerprint input transducer or sensor, the finger under investigation is usually pressed against a flat surface, such as a side of a glass plate, and the ridge and valley pattern of the finger tip is sensed by a sensing means such as an interrogating light beam.
Various optical devices are known with employ prisms upon which a finger whose print is to be identified is placed. The prism has a first surface upon which a finger is placed, a second surface disposed at an acute angle to the first surface through which the fingerprint is viewed and a third illumination surface through which light is directed into the prism. In some cases, the illumination surface is at an acute angle to the first surface, as seen for example, in U.S. Pat. Nos. 5,187,482 and 5,187,748. In other cases, the illumination surface is parallel to the first surface, as seen for example, in U.S. Pat. Nos. 5,109,427 and 5,233,404. Fingerprint identification devices of this nature are generally used to control the building-access for information-access of individuals to buildings, rooms, and devices such as computer terminals.
In capacitive fingerprint imaging devices, a fingertip is pressed against an array of sensing electrodes. Each electrode forms one of two electrodes in a capacitor. Each capacitor is generally pre-charged to provide a known voltage. The placement of the fingertip on the sensing electrodes results in changes to the induced voltages or capacitances and therefore allows for imaging of the fingerprint. Devices of this type are well known in the art.
The use of random numbers has become popular in many aspects of computer science. An annealing algorithm generates and entire process based on an initial random seed. The seed allows the process to be repeated, but its random nature allows the annealing process to run differently each time. In encryption technology, random keys are also used for generating private and public keys. Unfortunately, computers are only capable of generating pseudo random numbers. These numbers may follow known sequences for they may rely on date and time information making them predictable.
Several electronic approaches to random number generation have been proposed. It is known to use a resistive circuit that generates a voltage or current to be measured that lies at an exact value. Voltages above and below the value are interpreted as a one and a zero, respectively. Of course, it will be apparent to those of skill in the art that the selection of one to be above the threshold is arbitrary and that the respective interpretation can be otherwise. The random nature of the binary value is ensured based on the laws of quantum physics. Unfortunately, such a system is influenced by external factors such as temperature, humidity, etc. Also, electronic random number generators for use with a computer are often costly.
When conditions change, existing devices often become unreliable. For example, a resistance based device often produces a sequence of "random" numbers of a dubious nature when temperature changes are significant. As is well known, this is often the case within computer systems, where bright lights are used, near doorways, in electronic devices, in automobiles, and so forth. As such, as more flexible random number generating device and method is needed.